The present invention relates to an improved system for the operation of a plunger lift or "rabbit" oil and gas well. The invention also relates to an actuator mechanism for selectively positioning a choke valve element relative to a valve seat within a piping flow tee for regulating the flow of gas and oil from the tubing string of a plunger lift well.
A plunger lift well has an outer casing and an inner tubing string. The casing is a barrier between the strata through which the well was drilled and the annular area of the drilled hole. The casing is perforated at locations within the source rock for passage of gas and oil into the annular area of the casing. The tubing string extends coaxially down the casing and terminates generally at the source rock. The lower end of the tubing string is formed to provide a stop or seat for a lift plunger. Delivery of gas and oil from the tubing string is selectively controlled by the system and actuator mechanism of the invention.
A lift plunger is a solid bar, 12" to 18" in length, having an outer diameter less than the inner diameter of the tubing string and free to move up and down the tubing string in response to pressure differentials between the casing and the tubing string. Well gas entering the annular area of the casing through the perforations causes a buildup of gas pressure within the casing. The increase in casing gas pressure causes gas and oil within the casing to enter the annular area of the tubing string through the open lower end. The rise of an oil column within the tubing string and above the plunger, toward the wellhead, is selectively controlled, at the option of the well operator, by a "low stage" setting of the actuator mechanism of the invention. The "low stage" setting vents gas in the tubing string through the wellhead piping flow tee. The plunger will remain at the bottom of the tubing string.
When the pressure differential between the casing (high) and the tubing string (low) has reached a value, as established by the well operator, a "high stage" setting of the actuator mechanism of the invention will reduce the pressure above the oil column in the tubing string and the plunger will rise forcing the oil above the plunger through the wellhead piping flow tee.